The invention is based on a centrifugal adjuster as generally defined hereinafter. By means of the centrifugal adjuster, the speed governor of the fuel injection pump is supplied with the engine rpm as an actual value in the form of a regulating travel; on this basis, along with an evaluation of the load, which is also to be supplied to the governor, the injection quantity and thus the set-point rpm are regulated. In this kind of centrifugal adjuster, the flyweights, as they rotate are engaged by rpm-dependent centrifugal force, which is transmitted to an adjusting sleeve via bell cranks joined to the flyweights; the sleeve is engaged by a spring that acts counter to this force, so that the regulating travel of the sleeve corresponds to the centrifugal force. The prestresssing of the spring engaging the sleeve can be varied by the governor as a function of load, so that the regulating travel of the sleeve then corresponds to both load and rpm.
This speed governor connected to the centrifugal adjuster has a governor rod, on the lever of which various bearing positions are provided; there are also bearing positions of one lever on the shaft of another lever. The cooperation among the levers, some of which have variable operative lengths, becomes quite complicated, and the bearing positions are subject to a variably severe amount of friction. This friction transmitted to the governor causes hysteresis in governing, which has a disadvantageous effect on engine operation. A Coulomb friction of this kind produces low-frequency rpm fluctuations, on the order of approximately 2 Hz, during engine idling. This governor error, which causes engine "seesawing", has a particularly pronounced effect during idling, because in that state only small fuel quantities are metered, and so slight differences in quantity, whether in terms of fuel metering or fuel consumption, have a very marked effect, and further it is well known that deviations of 30% from the set-point quantity can arise in the quantity metered to or consumable by each engine cylinder. In dynamic terms, these differences have a correspondingly extremely brief influence on engine speed and hence, via the speed governor, on the injection quantity. Depending on which engine cylinder the variation in injection quantity may be applicable to, this can cause an undesired increase or slowing down of the mean rpm that is to be established by governing. The result may be that at desired idling speeds of 600 rpm, the deviation may be more than 200 rpm, which causes the above-mentioned unsteady engine operation known as "seesawing".
As is well known, a Diesel engine has a considerable degree of rotational irregularity or imbalance or non-concentricity, which is due to various factors, and it can be only partly compensated for by providing a flywheel. This non-concentricity of the engine produces vibrations in the range between 20 and 40 Hz, depending on the mean rpm and the number of cylinders. While it is still possible to control rpm fluctuations, resulting from the degree of non-concentricity, by providing specific means of damping them or by maintaining them in part and transmitting them to the governor accordingly, such control is no longer attainable for the seesawing vibrations, which are additionally superimposed on the others. The only product of the seesawing frequencies is noise, that is, interference, and so it becomes desirable to eliminate them to the greatest possible extent.
The drive shaft of the centrifugal adjuster, which in the case of an in-line injection pump for instance is the camshaft, is driven directly by the engine, so that the degree of non-concentricity is transmitted directly to the driving part of this centrifugal adjuster. In a centrifugal adjuster of the above generic type, a torsionally elastic coupling is therefore provided between the driving part and the flyweight holder, and depending on whether the acceleration of a given rpm is positive or negative this has the effect that the flyweight holder is in advance of or trails behind the rotational movement of the driving part, so that because of the torsionally elastic connection, a positive or negative rotational angle relative to a mean position is attained.
In a known centrifugal adjuster of this generic type (Swiss Pat. No. 21 42 49), rubber-elastic elements serve as the torsionally elastic coupling, each of them supported on one side on the driving part and on the other on the flyweight holder. By means of this kind of torsionally elastic coupling, the positive and negative rotational angle relative to the flyweight holder, superimposed on the rotational movement because of the degree of non-concentricity of the engine, is damped; the disadvantage of this is that because of hysteresis the rpm governor develops greater friction, particularly in idling, and thus becomes more sluggish and less accurate; the effect of this is an increase in the seesawing fluctuation during engine idling.
Another known centrifugal adjuster (German Pat. No. 21 13 571) has as its elastic coupling a friction coupling, which exhibits increasing friction as the angle of rotation increases and has a spiral spring for adjusting the initial rotational position of the two parts relative to one another; this spring engages the driving part on the one hand and the flyweight body on the other. With this elastic coupling, severe damping of the transmission of the degree of non-concentricity in the rotation is once again attained, which is intended to prevent torsional vibration on the part of the injection pump governor, which could interfere with the governor characteristic. The disadvantage, however, is that this also increases the hysteresis of the rpm governor during idling, which still has a large number of bearing locations and masses; the effect, in particular, is an increase in seesawing vibrations.